Motor vehicles today are equipped with highly sophisticated electronic systems. The 12V batteries typically found in motor vehicles provide a ready source of electrical energy for such systems, but the battery voltage is generally too high and also quite unstable. Buck-type switching mode power supplies (“SMPS”) are therefore sometimes used to convert the vehicle battery voltage to the lower, more stable voltage needed to power a particular system or subsystem. This type of SMPS receives the unregulated battery voltage and converts it into stable direct current power at a lower voltage of, e.g., 5V or 3.3V. SMPS which perform this type of voltage conversion are referred to as a ‘buck’ type SMPS because the supply voltage at the output of the SMPS is lower than the source voltage at the input to the SMPS. For the remainder of this document SMPS shall refer to ‘Buck’ type SMPS.
Some electronic systems used within motor vehicles are sensitive to radio frequency noise such as radio frequency interference (“RFI”) and electromagnetic interference (“EMI”). It is therefore desirable that all systems used within the motor vehicle, including any power supplies, be carefully designed to contribute as little high frequency noise as possible.